Drier felt for paper machines and the like



July 14, 1936. w. A. BARRELL DRIER FELT FOR PAPER MACHINES AND THE LIKE Filed Feb. 15, 193s Patented July -14, 1936 UNITEDSTATES PATENT OFFICE DRIEB FELT FOB PAPER MACHINES AND THE LIKE William A. Barrell, North Andover, Mass. Application February 13, 1933, Serial No. 656.446 8 (Cl. 139-410) heated metal drying drums, over and aroundA which the web passes until it dries sumciently for calendering. It is the purpose of the present invention to provide an improved drier felt having capacity for longer useful life than those heretofore made; one having greater porosity, particularly in the back or outer ply, and greater eillciency for absorption of water from the paper and evaporation of the absorbed water; and one which will stretch less in length and retain more nearly its original width under like conditions of service. These objects are accomplished by the novel construction of the drier felt hereinafter described, and by equivalent constructions within the scope of the appended claims.

In the drawing furnished herewith to illustrate the invention,-

Fig. l is a plan view of a fragment of my new drier felt as seen looking toward the face of the felt;

Fig. 2 is a longitudinal section taken on line 2 2 of Fig. 1;

Figs. 3 and 4 are cross sections taken on lines 3-3 and 4--4 respectively of Figs. l and 2. These views are shown on a somewhat enlarged scale;

Figs. 5-8 are diagrammatic views on a larger scale to show the construction more plainly, and

' are represented with the constituent strands widely separated. Of these, Fig. 5 is a face plan view, Fig. 6 a plan of the rear or underside, and Figs. '7 and 8 are sections on lines 'I-l and 8 8 respectively of Fig. 5.

Like reference characters designate the same parts wherever they occur in all the gures.

It will be assumed for the purpose of the present description, but without intent to limit the invention to a speciiic material, that all the strands of the felt are of cotton composed of a number of single strands or yarns twisted together to give adequate bulk and strength. Iy

may use yarns of the same weight as are commonly used in the commercial felts manufactured under the said Barrell patent, or larger or smaller strands as desired.

'I'he face ply of the felt is composed of structural or body warp strands a and b in repeated alternation, interwoven as a plain weave with filling strands c and c'; the strands or ends a of the warp passing over the picks c and under the picks c' of the filling, and the warp strands b passing under the picks c and over c. Similarly the back or outer ply is a plain weave consisting of warp strands d and e, alternating with one another, and filling or weft strands ,f and f in alternation. 'I'he two plies of the fabric are tied together by binder strands o which run parallel with the warp. 'I'hese binder strands pass over two picks c and c' of the illling in the face ply, then under one pick f' of the filling in the rear ply, then over the next two picks c and c of the face ply and under the next pick f of the back ply; and so on, overlying all the filling strands of the face ply but crossing only every other filling strand of the back ply. All of the binder loops are interlocked with the same illling strands f' and the intermediate strands are clear of binders. As here shown, binder warp strands alternate with all the body warp strands of both plies; that is, there are as many binder warp strands g as body warp strands a and b combined, or body warp strands d and e combined, and each body warp strand in each ply is flanked by two of the binder warpstrands. In a specific design of felt, where eight each of 'the warp strands a, b, d, and e are provided for each inch of width, there are sixteen of the binder warp strands per inch.

All of the warp strands are so large, or conversely so numerous in proportion to their thickness, that they are closely crowded together. The binder warp strands are preferably of the same weight, thickness and density as the body warp strands, but may be larger and/or denser. They are woven under less tension than thel body warp strands. In the course of weaving they are held up by the harness above the shuttle path while two picks of filling are placed and beaten up in the face ply and the shed of the face ply warp is changed between the placement of such picks; and they are then brought to the back ofl the felt and bent around a single pick of filling in the back ply together with half the warp strands of that ply. They are raised above the face ply again between the pick c' of illling last placed therein and the next pick c. In consequence of these factors, those portions of the binder warp strands which overlie the filling strands of the face ply also overlie the body warp strands of that ply, to a considerable extent, and protrude beyond them, as shown by Figs. 3 and 4, forming a substantially, or nearly, continuous surface on the face of the felt, while the same binder strands also embrace, and tie in, alternate filling strands of the back ply. The side which is thus referred to as the face of the felt is that which contacts with the paper, and is the only one which does so; and the binder warp strands where they lie exposed on this surface are the 5 only members which touch the paper. They lie so near together that they do not indent the paper to an objectionable extent; that is. they do not make so-called felt marks too deep to be obliterated by calendering. But if desired they may be flattened more or less by pressure.

A felt having the construction above described, and woven exactly according to the practice used in making the commercial two-ply felts, except that the binder warps are maintained under less tension than the body warps in weaving, and under only enough tension to lead them-smoothly and without slack through the fabric, is a complete embodiment of one phase of the invention. Even in the absence of other factors, later described, it has conspicuous utility and advantage over prior constructions.

It is more porous, due largely to the open construction of the back ply in which open spaces are left between the body warp strands across and beside each of the filling picks f which are not embraced by a binder. Also spaces exist in the face ply wherever a binder passes over a pick of the filling while the adjacent body warp strands pass under the same pick. This facilitates the escape of water vapor from the paper being dried. In so far as the binder strands are absorptive of water, their loops which pass through the back ply serve as conductors to lead water by capillary action to the exposed back of the felt and into adjacent structural strands, which release moisture by evaporation into the air of the room.

'I'he binders on the face of the fabric prevent the body warp strands of the face ply from coming into contact with the hot damp paper, and

40 thus protect these warp strands, as well as those of the back ply, from the destructive effect of high temperature. Thereby the body warp strands of the face ply retain their strength and take their part of the load in pulling the felt around the drying drums and guide rolls for a longer time. Even though the tensile strength of those parts of the binder which lie on the face of the felt be utterly destroyed by the burning and rotting effects of high temperature and moisture, this does not diminish their serviceability, for they are not relied on in any degree to lend tensile strength to the felt, and they are not put under tension by the strain which is applied to the felt when running. The only mechanical function they per- P form is to tie the two plies together; but the forces tending to separate the plies are negligible in terms of tensile stress applied to the binders, and anyway those parts of the binders which pass through the felt from front to back 60 are protected, and are so gripped by the body warp strands on opposite sides of them, somewhat as a nail driven into a board is gripped by the fibers of the wood, that they are still serviceable to perform their connecting function even though the face loops be burned or rotted so much as to have no strength at all.

Another phase of the invention consists in means to prevent stretching of the felt and narrowing of its width in service. In the ordinary course of weaving the filling is laid with no more tension than is caused by drawing off from the shuttle bobbin as the shuttle is thrown through the warp shed. Each pick of the filling therefore lies in a straight line and the warp strands are bent sharply around it when the shed is changed. Tension exerted on the finished felt tends to straighten these bends in the warp strands and to compress and displace the filling into the spaces between warp strands on the other side. In so far as such compression and dis- 5 placement of the filling is possible, the felt is elongated; while the bending of the lling which then takes place crowds the warp strands together laterally and reduces the width of the felt. This is the cause of the stretching and narrowing 10 of drier felt which always takes place in service. The total length of the warp strands is not increased, for they are of such closely twisted construction and interlocked by the weave at such close intervals that they cannot stretch; but the 15 elongation of the felt as a whole is due entirely to the partial straightening of these deep bends.

It is the practice therefore to manufacture felts with excess width sumcient to allow for the expected narrowing, and to provide the drying ap- 20 paratus with take up rolls to absorb the slack due to stretching of the felt. When the stretch becomes greater than the capacity for adjustment of the take up rolls, as not infrequently happens, a piece must be cut out of the felt and the ends 25 joined together again.

I have devised a means to prevent in large measure this stretching and narrowing of felts in practice, which is embodied in the felt here illustrated and is a phase of the present inven- 30 tion. This means consists in making the filling pliable before weaving, by wetting it with a suitable liquid, and applying such tension to the body warps that, in the course of changing the shed, they initially compress and displace each 35 pick of the filling between each warp strand on one side and the two flanking warps on the other side of the filling strand. Thus the felt as it comes from the loom has less bend in the warp strands, and the possible scope for crimping of 40 the filling strands is already largely taken up, wherefore the felt has less liability to stretch or become narrower in width under like conditions of service. The length of warp in a finished felt so made is less than that in a felt of the saine 45 construction woven with dry filling, wherefore a felt of a given length weighs less and can be sold to the consumer at a lower price, other things being equal. A felt of given length and width may be put on the drier with assurance that it 50 will neither become narrower than the paper web nor stretched beyond the capacity of the take up rolls to absorb the slack.

'I'he liquid used for wetting the filling may be water alone, or any solution which will pene- 55 trate cotton yarn more readily than water, and is not injurious, but I may use, and therefore claim as a factor of the invention, a liquid which is also a waterproofing agent. I may use any one of a number of compounds or substances which 60 are suitable for the purpose of both making the filling pliable and waterproofing the felt. One suitable agent is aluminum acetate in a solution of 4 Twaddle, which I name as an illustration, Without limiting intent as to the substance or its 65 concentration in the solution. It is absorbed from the saturated filling strands by the adjacent warp strands and, on drying, waterproofs the entire structure.' A ,felt so waterproofed, when made'of the porous construction herein 7o described, does not absorb any considerable quantity of moisture from the paper, and therefore does not necessitate expenditure of heat to be itself dried, but permits escape of water vapor from the paper through its interior passageways. 75

While I have herein described the felt as being made entirely of cotton strands, I wish to make it understood that I am not limited to cotton as the material of all or any of the strands, but may use other materials suitable for the purpose. Such suitable materials are any which have adequate strength and pliability, including not only those which have been heretofore used in drier felt manufacture, but others which may by test and experience be hereafter found satisfactory. Strands or fibers of such other suitable materials may be combined with cotton strands or with one another as either the body warp or the illling of either or both plies, or for the binder strands.

It is to be understood that the scope of my claimed protection embraces the drier felt in all uses which it is adapted to serve.

What I claim and desire to secure by Letters Patent is:

1. A drier felt for paper machines comprising two complete plies constructed each of interwoven warp and filling strands, and binder strands supported externally on the exposed parts of the warp strands on the outer face of one ply, whereby they overlie and protect the warp strands of that ply, and having loops at intervals extending through the felt in interlocked connection with strands of the other ply to exposed points on the outer face of the latter ply.

2. Adrier felt for paper machines comprising two complete plies constructed each of interwoven warp and filling strands, and binder warp strands interwoven with filling strands of both plies and protruding on the paper-contact face of the felt beyond the ply warp strands so as to overlie and protect said ply warp strands.

3. A drier felt for paper machines comprising two complete plies constructed each of interwoven structural warp and iilling strands, and

binder warp strands, each passing over all the.

illling strands of the face ply and protruding outside of the warp strands thereof, so as to provide the paper-contacting portions of the felt,

" and having loops passing between structural warp strands of both plies-and being interlocked with filling strands of the back ply.

4. A drier felt for paper machines comprising two complete plies constructed each of interwoven structural warp and filling strands, and binder warp strands, each passing over all the filling strands of the face ply and having loops passing between structural warp strands of both plies and being interlocked with filling strands of the back ply: the parts of the binder warp strands which lie in the paper-contact face of the felt being supported by the contiguous structural warp strands so that they protrude beyond said structural strands in the face of the felt.

5. A drier felt for paper machines comprising a complete face ply constructed of interwoven warp and filling strands. a complete back ply ai'ter said outer stretches have lost constructed of an equal number of like warp and filling strands as the face ply, and binder strands; said binder strands extending in parallel over the same two adjacent nlling strands of the face ply, then through the felt in alternation with the structural warp strands of both plies and around a single lling strand of the back ply, then through the felt and over the next two filling strands of the face ply, around a third tilling strand of the back ply, and so on throughout the length of the felt, said warp and binder strands being soclosely crowded together that those parts of the binder strands which cross illling strands of the face ply protrude beyond the warp strands of that ply.

6. A porous drier felt for paper machines comprising two complete plies each constructed of interwoven structural warp and filling strands, and binder warp strands lying outside of and in protective covering relation to the structural warp strands of the face ply of the felt and having loops passing through the felt into exposure to the atmosphere at the back of the felt between successive groups of filling strands of the face ply, at each side of each of the structural warps in both plies, and around non-adjacent filling strands of the back plyi 7. A drier felt for paper machines comprising plies of interwoven warp and filling strands of vegetable fiber essentially non-shrinkable by fulling, and binder strands interwoven with filling strands of both plies alternately, each of `said binder strands extending across all of the filling strands in successive groups, of one ply, and somewhat covering the warp strands of that ply so as to contact with the paper being dried and 4 prevent contact between the paper and said warp strands: and the binder strands also passing through both plies and around non-adjacent picks of the other ply, forming loops which are exposed on the back surface of the latter ply.

8. A drier felt for paper machines comprising a face ply and a back ply, each woven of vegetable warp and lling strands in a single piane weave, additional warp strands interwoven with both plies; said additional warp strands having stretches lying on the outer face of the tace ply, each stretch passing over at least two adjacent illling strands of that ply and being supported by the contiguous body warp strands so as to overlie and protect said body strands from contact with the paper being dried; and the additional strands also having loops which embrace non-adjacent illling strands of the back ply, each loop passing through the face ply between adjacent lling strands and contiguous body warp strands thereof and being closely embraced and gripped by said contiguous warp strands, whereby they are enabled to couple the plies together tegi'ity.y

WILLIAM A. BARRELL. 

